The invention relates generally to alloys, and specifically to alloys to make a gold colored alloy hard enough for jewelry and dentistry. In addition, this alloy should provide a material with the addition of silicate which does not easily tarnish.
Gold jewelry and utensils are valued because of their intrinsic worth and the gold color of the metal. For example, an alloy called astrolite(trademark) was produced which comprises of silver, palladium, gold, and indium for commercial use, which is the subject of a U.S. Pat. No. 4,350,5427. However, a lower cost gold alloy is desirable.
U.S. Pat. No. 5,134,039, Alexander, discloses a metal article comprising a metal selected by the group consisting of copper, silver and gold, another metal selected from the group consisting of zinc and a plurality of ultra fine particles having an average particle size of less than about 20 microns dispersed substantially evenly through said metal article. Wherein the ultra fine particles are water insoluble metal silicates. The invention is described as providing a process for the electrodeless plating of easily removable metals onto ultra fine usually inert particles.
U.S. Pat. No. 4,948,557, Davitz, discloses a gold-colored alloy for jewelry and dental purposes and the like consisting essentially of 24 to 27 percent palladium, 19 to 22 percent indium, 5 to 30 percent copper, 1 to 20 percent gold and the balance of silver. While gold, silver and copper are present, the additional constituents of palladium and indium teach away from the present invention, as does the absence of metal silicates.
U.S. Pat. No. 5,019,335, Davitz, discloses a gold-colored metal alloy consisting of 75 to 85 percent copper, 5 to 15 percent nickel, 0 to 12 percent indium and 0 to 12 percent zinc. It is also being indicated as being desirable to add approximately 0.01 percent iron and/or 0.05 percent silicon and to act as a grain refiner and fluidity enhancer, respectively. Thus, an alloy is disclosed that has a high copper content as well as zinc and silicon. However, nickel is present and indium may be present. Gold and/or silver are not present unlike the present invention.
U.S. Pat. No. 5,330,713, Davitz, discloses a gold-colored alloy which includes 6 to 20 percent by weight gold, 5 to 10 percent by weight indium, 5 to 12 percent by weight palladium, 23 to 40 percent by weight copper, 5 to 10 percent zinc and 23 to 40 percent silver. While gold, silver, copper and zinc are present, metal silicates are not present.
U.S. Pat. No. 3,925,066, Kohrn, et al., discloses a tarnish resistant Au/Ag alloy of low gold content exhibiting properties desired in jewelry manufacture consisting essentially of about 25 to 30 percent, by weight, gold, about 45 to 57 percent, by weight, silver, about 18 to 25 percent, by weight, of a metal selected from the group consisting of copper, nickel and mixtures thereof and 0 to about 5 percent by weight zinc.
U.S. Pat. No. 4,264,359, Harris, et al., discloses an alloy suitable for use in fabricating jewelry consisting essentially of about 25% by weight gold, about 11.75% to 12.60% by weight palladium, about 9.75% to 12.10% by weight silver, about 8.90 to 10.25% zinc, and about 0.045% to 0.065% by weight boron, balance copper.
U.S. Pat. No. 4,370,164, Harris, et al., discloses an alloy consisting essentially of 4% to 10% by weight gold, 54% to 61% by weight silver, 14% to 19% by weight copper, 4% to 7% by weight palladium, 9% to 14% by weight indium, 1% to 3% by weight zinc and 0.015% to 0.04% by weight boron.
U.S. Pat. No. 4,446,102, Bales, discloses the alloys comprising of 17-25% by weight gold, 10-27% by weight silver, 40-60% by weight copper, and 3-12% by weight zinc.
In accordance with this invention, an alloy is provided which contains Gold, Copper, Silicon, Silver and Zinc. This alloy will have a higher tarnish resistance and will be a harder alloy. In a 5% chlorine atmosphere, the present invention with silver is found to be superior to other low percentage of gold alloys; in fact has shown no discoloration. The corrosion resistance of this alloy is due to the addition of the silicate and gold.
An additional object of this invention is the production of an alloy mixed with gold and silver using zinc, a small amount of copper for hardness, and a small amount of silicate. This increases corrosion resistance and provides better working properties by reducing brittleness while still producing a low cost alloy.
Other objects of the present invention and advantages accruing therefrom, will be apparent to one who is skilled in the art from the following description. All percentages referred to are percent by weight, based on the total weight of material or mixture.